The long term objective of this research is to understand how Epstein-Barr virus (EBV) enters the B cell. The very restricted tropism of EBV is largely determined by a specific receptor, which is apparently exclusive to B lymphocytes. Binding is, however, not sufficient to induce virus penetration since cells exist which can bind but not internalize virus. There is also evidence to suggest that virion membrane proteins play a role in internalization of virus, beyond that of adsorption to the cell receptor. The specific aims of this proposal are to examine the optimal conditions for viral entry, the site(s) at which the envelope is lost, and the influence of virion and cell membrane components on the process. Optimal conditions for adsorption and penetration of virus will be determined by use of intrinsically radiolabelled virus. A combination of autoradiography, immunoelectron microscopy, ESR spin labeling and lysosomotropic reagents will be used to determine the site at which virus loses its envelope. The role of the EBV receptor in internalization of virus will be examined by comparison of receptor, immunoprecipitated from cells which bind virus and cells which both bind and internalize virus. Nearest neighbour analysis of receptors on the two types of cells will be performed and the effects of enzyme inhibitors on viral uptake will be determined. Influence of virion proteins will be probed by use of monoclonal antibodies. In particular the influence of antibody to the viral glycoprotein gp85, which fails to inhibit virus binding but neutralizes infectivity, will be examined. Epstein-Barr virus can induce infectious mononucleosis, may play a role in the etiology of Burkitt's lymphoma and is probably responsible for a significant proportion of fatal lymphoproliferative disorders in people with congenital or acquired immunodeficiencies. An increased knowledge of the early events in EBV infection is relevant both to basic virology and cell biology and may suggest new approaches to anti-viral chemotherapy.